Chapter 40Immune System

Mr. KarnsBiology

Color Coding• Red – most important• Orange – next most important• Yellow – it is o.k. to write it down• White – you likely do not need to write it down

• Taking notes is about deciding what is important and deciding if you can look it up later or not

Infectious diseases• Pathogenic (disease-causing)

• Methods of transmission– Airborne droplets: chicken pox, flu, influenza– Direct contact: cold sores, Hepatitis B, C Exchange of bodily fluids: STD’s – HIV/AIDS, syphillis, gonorrhea

– Objects Contaminated H2O: polio, cholera

Contaminated food: botulism, E. coli (some strains only)– Vectors: Lyme disease (ticks), malaria (mosquitoes), bubonic plague (fleas)

SNEEZE VIDEO

• Just Watch and Enjoy

Determining cause of a disease

Koch’s Postulates

• [Note: This method doesn’t work with syphilis organisms nor viruses.]

• (Viruses can’t be grown outside of a living cell, so #2 above won’t work)

1. Identify pathogen every time2. Isolate & grow3. Infect healthy organism4. Isolate from new host (and grow it again if you need to)

SCIENTIFIC METHOD - Koch’s Postulates

Reservoirs of infectious organisms

• Human beings • Carriers: people who contain pathogens

and pass them on to others before any symptoms show in themselves.

•Incubation period = time during which organisms are multiplying and before any symptoms show up.

• Animals– Birds, insects, mammals

• Soil– Botulism and tetanus bacteria, anthrax (or in poorly processed canned food)

What do pathogens do to cause disease?

• Bacteria produce toxins– Cause fever, inhibit protein production,

destroy RBCs and blood vessels, cause spasms (by disrupting nervous system impulses)• Ex. tetanus toxin: causes uncontrolled muscle

contractions -- eventually paralysis and death

• Viruses multiply in cells, lyse (burst) some cells as they multiply and thereby injure tissues.

Spread of diseaseknow these three terms

• Endemic disease: low-level of infection which is constantly present in a population

• Epidemic: a localized outbreak of a disease– Polio outbreak during 1950s

• Pandemic: world-wide outbreak of a disease– Influenza of the early 1900s

How to treat infections• Antibiotic: chemical substance produced

by a microorganism which can inhibit the growth and reproduction of other microorganisms.– Produced by many bacteria and fungi,

sponges– Work on gram positive bacteria– Cause the cell wall to breakdown (lysis)

• Nothing good available to inhibit viruses (AZT is a reverse transcriptase inhibitor used to treat HIV infections with AIDS)

A Potential Problem• The overuse of antibiotics kills off all the

sensitive pathogens -- only the mutant resistant pathogens remain to repopulate.

– Penicillin-resistant syphillis organisms (produce penicillinase)

– Drug-resistant strains of tuberculosis bacteria already exist

Non-Specific Immunity1. Skin2. Inflammation3. Phagocytosis (Innate Immunity)

a. Macrophages (1st line phagocytic defense)b. Neutrophils (2nd line of phagocytic

defense)c. Monocytes (3rd line of phagocytic

defense)

Nonspecific immunity

• Innate immunity: “inborn” immunity– 1. Skin

•Physical barrier•Secretions (skin, nose, lungs, etc.)

– Mucus– Sweat (some enzyme lysozyme)– Tears (much enzyme lysozyme) (Alexander Flemming

discovered)

– Saliva (some enzyme lysozyme)– Gastric juice (HCl and other chemicals kill lots of

bacteria)

the skin has a pH between 3 and 5, which is acidic enough to prevent colonization of many microbes

• 2. Inflammation process– Caused by Histamine release!– a. Reddening of area because blood vessels dilate– b. Swelling c. Pain d. Heat

Phagocytes• Phagocytes are white blood cells that

ingest and destroy pathogens.

• What are the three phagocytes?

Phagocytosis is– the process by which phagocytes ingest

and destroy pathogens

• 3. Some White blood cells are phagocytes (“eating” cells)

– Tissue macrophages (“big eaters”)

– Neutrophils (WBC) can phagocytose bacteria– Monocytes (large WBC which become macrophages)

– Macrophages and neutrophils die after “eating” pathogens; along with dead tissue cells and plasma, they make pus!

Phagocytosis Video

Puncture Wound Video

Be prepared to draw a diagram of the process!

Lymphatic system• Lymph

capillaries • Lymph vessels• Lymph Nodes• Thymus

– T cells mature

• Spleen– Storage of WBC

& RBC

• Tonsils

Purpose of Lymph System

• Return tissue fluid (previously blood plasma) back to heart and into circulation

• Tissue fluid is called lymph once it enters lymphatic vessels

General arrangement of capillaries and lymphatic vessels (green)

Lymph nodes

• Contain lymphocytes (WBCs) which...– Defend body against foreign

substances

• Filter lymph of most bacteria

White Blood Cells = Leukocytes• Phagocytes:

– Macrophage– Neutrophil– Monocytes

• Lymphocytes– T cells (Helper, Cytotoxic and Memory T-

cells)• Mature in the thymus

– B cells (Memory B cells and plasma cells)

RED and WHITE blood cells are produced in bone marrow

Specific Immunity• Acquired Immunity

– Passive– Active

•Antibody Immunity (Humoral Immunity)•Cellular Immunity (for viruses, cancer

cells, tumors)

Antibodies react with antigens and do several

things

Antibody (humoral) Immunity

Be prepared to draw the process of humoral immunity.

.Helper T cells are important !

.Cytotoxic T cells are Killer T cells

Steps of Antibody Immunity

Displayedantigens

Cellular Immunity for Viral Defense

Be prepared to draw the process of cellular immunity

Draw a diagram of the cellular immune response.

You may work in groups of three, but everyone needs to draw the diagram.

Cellular Immunity

(Cytotoxic = Killer)

Lesion = opening

Perforin = cluster of proteins which make a Lesion (hole).

– Produced by virus-infected cells– Interferons are host-specific (human

proteins only work for humans, etc.)– Interferon act as an “alarm” molecule to

uninfected cells– Uninfected cells produce antiviral proteins

which prevent viruses from entering them.

[Summary note: cells of innate (nonspecific) immune system constantly monitor tissues for foreign invaders and attempt to suppress the “invasion”.]

Interferon Proteins

Allergy (can be specific or non-specific)

• Is an exaggerated reaction to antigens

• A 2nd exposure to an environmental Ag causes the typical allergic reaction– Histamines affect

tissues throughout whole body similar to an inflammatory reaction.

(pollen grain)

• 1983: HIV -- is a retrovirus (RNA virus; contains reverse transcriptase to reproduce itself in a host cell)

• HIV infects and kills helper T cells• Nearly all HIV carriers will have AIDS and will

die from cancers or opportunistic infections.

HIV structure and infection of helper T cell

HIV / AIDS / Immune System• 1981: rare types of pneumonia and skin

cancer (Karposi’s sarcoma) noticed in San Francisco– Nonfunctioning immune systems in patients

Purple splotches common in Karposi’s sarcoma

HIV budding from helper T cell

HIV

End

It’s time for TEST Review

1. A general type of “eating” cell is called a __________ .

2. A specialized type of big “eating” cell in the immune sytesm is called a ________ and is usually considered to be part of nonspecific immunity.

phagocyte

macrophage

3. AIDS is a disease of the immune system because HIV infects and kills the ___________ cells which are important in developing an immune response.

4. Organ transplants procedures require the patient’s immune system to be suppressed before the procedure begins? Why?

Helper T

To prevent cellular immunity methodsfrom rejecting the donated organ.

Easyquestions

Question 1 Diseases that are constantly present in the population are called _____

A. endemic diseases B. epidemic diseases C. immunity diseases D. resistant diseases

Question 2 Who first proved that a specific microbe

caused a particular disease? A. Jenner

B. Mendel C. Darwin D. Koch

Question 3 While in the lymphatic vessels, tissue fluid passes through structures called _____ that filter the fluid.

A. lymphocytesB. lymph nodesC. thymus glandsD. mucus traps

Question 4Which of the following are part of the

nonspecific defense (innate immune system) against diseases? A. B cells B. T cells C. plasma cellsD. macrophages

Question 5 Which cells are attacked by HIV?

A.B cells B. T cells C. plasma cells D. macrophages

Medium Difficultyquestions

Question 1 A baby is born lacking a thymus gland.

What cells are missing in the child? A.B cells B. T cells C. plasma cells D. macrophages

Question 2What is the relationship between tissue fluid and lymph?

A. Tissue fluid leaks out of blood vessels and is called lymph when it enters lymphatic

vessels.B. Tissue fluid surrounds the body cells, and

lymph circulates throughout the body in the lymphatic system.

C. Lymph leaks out of the blood. It is thencalled tissue fluid.

D. Tissue fluid is the liquid portion of the blood. When it leaks out of the capillaries, it is called lymph.

Question 3What is the function of a booster shot?

A. Some individuals are allergic to the first

shot, so they need more than one shot.

B. The booster vaccines contain different

materials.C. When the body is re-exposed to a

disease agent, it forms more memory cells for immunity.

D. A booster shot will activate different cells of the immune system from those activated by the first

vaccine.

Question 4Why do patients with AIDS continually battle infectious diseases?

A. AIDS patients are infected with the HIV virus.

B. AIDS causes the production of interferon.

C. AIDS destroys the plasma cell response to infectious diseases.

D. AIDS weakens a patient's immune response to infectious

diseases.

Question 5 Why does a vaccination give long-lastingprotection against a disease?

A. Vaccines increase the level of antibodies in the bloodstream.

B. Vaccines contain dead or weakeneddisease agents.

C. Vaccines prevent the body from responding to disease agents.

D. Vaccines cause the body to create memory cells that are prepared to

fight any future encounters with the disease organism.

Difficultquestions

Question 1 (analogy)Virus-infected cells are to interferon

as plasma cells are to _____A. complement B. lysozyme C. antibody D. helper T cells

Question 2When a patient receives a kidney transplant, the patient's immune system is suppressed by the use of prescribed drugs. Why would this be important and necessary?

A. Without this suppression, the immune system would attack the foreign

transplanted tissue.B. The suppression will stimulate the immune

system to work more efficiently.C. The suppression will stimulate the bone

marrow to produce more white blood cells.D. Without the suppression, the body will

secrete too many hormones.

Question 3Why might a physician recommend against taking a fever-reducing medication when you have an abnormally high temperature?

A. A high temperature activates the immune system.

B. A high temperature inhibits the growth of some disease-causing bacteria.

C. A high temperature decreases blood flow, so the disease will spread

more slowly.D. A high temperature inhibits the

body'srepair.

Do well on your test :)

That’s all . . .

A bit of a review and some detail follows.

Watch carefully I will move quickly.

Cellular immunity, cancer, & organ transplants

• Cytotoxic (Tc) cells will “lock onto” any cell which presents a “foreign” molecule– Virus-infected cells present an Ag in the midst of

their own self marker molecules (new markers are made continuously)

– Malignant cancer cells present unusual molecules which attract Tc cells; Tc usually keep cancer cells “in check”

• Some types of cancer lose their ability to continue making self marker molecules and don’t present the unusual molecules which ordinarily attract Tc cells.

– Transplanted organs may contain slightly different self markers and attract Tc cells

• Immunosuppressant drugs such as cyclosporin A are used before, during, and after the transplant procedure to avoid activation of helper T cells.

Acquired immune response

• Self components of a person’s own body– Self marker is a cluster of proteins on plasma

membrane surface; cluster is a “protein fingerprint” -- unique for each person (real term = major histocompatiblity complex)

• Foreign substances are nonself.– Nonself molecules are called antigens

• Pollens, dust particles, animal dander, bacteria, viral proteins, etc.

• Acquired immune response is a process of producing specific antibodies against specific antigens

• Acquiring immunity takes time (up to 2 weeks)

Thymus gland

• Immature lymphocytes mature into T cells

• Gland declines in size by adolescence

The Spleen

• Contains lymphocytes

• Filters and destroys bacteria

• Removes old RBCs from circulation; liver converts them into bile

Antigen-Antibody binding is specific

Two kinds of acquired immunity

• Antibody (humoral) immunity– Antibodies circulate in the blood (humor)

• Cellular immunity– Antibodies remain attached to immune

cells (lymphocytes)

– Acquired immunity is SPECIFIC and occurs simultaneously with Innate or non-specific immunity.

• Lymphocyte: basic cell of immune system– Made in red bone marrow from stem cells

TB

Specific immunity

• Occurs simultaneously with innate immune cells

• Certain white blood cells (lymphocytes) “learn” to recognize foreign substances and react specifically to them.– These cells can eventually inactivate/destroy

pathogens– This takes time (from days up to 2 weeks).

• Immunity which results is called acquired immunity.

– Two categories of lymphocytes•B cells -- have only been exposed to bone

marrow•T cells -- spend time in and mature in thymus

gland; receive additional attributes beyond B cells

– May circulate in the blood or reside in lymphoid tissues/organs

• T cells– Helper T cells interacts with Antigen-presenting

macrophages or Antigen-presenting B cells

M

a. Macrophage with ingested pathogen,b. In a food vacuole, c. Presenting pathogen

B

T

d. Helper T cell binds to macrophage self markers; T cells become stimulated by binding to the antigens on macrophagesT

Memory B Cells Clone

e. Activated T cells bind to B cells;f. B cells divide rapidly into plasma cells and memory cells

B Plasma cellsY

Y Y Y

YY

Y

Y

YYYY

YYY

Y

Y YAntibodies in blood and tissue fluid

B cells can bind antigens directly

B

T

Helper T cell releases chemical (interleukin) which activates B cell to divide.

Plasma cellsY

Y Y Y

YY

Y

Y

YYYY

YYY

Y

Y Y

Memory B Cells CloneYY

Y

Y Y YYY

From nonspecific defense to production of antibodies

Summary

Many B cellsto select from

Only one kind of B cell becomesactivated by a specific antigen

Most memory cellslast our whole life.

Primary/Secondary Responses

The complement cascade• Complement = about 20 proteins in blood

– Complement proteins self-assemble to make a lesion in plasma membrane; cell lyses

Examples of perforin lesions

Cancer cells

Two types of acquired immunity

•1. Passive: receive antibodies from another source -- person, animal,

genetically- engineered antibodies from bacteria– Ex. Antibodies from mother -- through the

placenta; through breast milk– Ex. Injection of pooled serum (from many donors)

and its diversity of antibodies from donors.

•2. Active: antibodies obtained naturally

by having an infection of a pathogen OR

– Receiving a Vaccine of . . .•Dead or weakened pathogens (viruses,

bacteria)• Edward Jenner (1798): use cowpox virus to

vaccinate against smallpox -- cowpox protein shapes are similar enough to smallpox to give immunity

• Which type of immunity is longer-lasting -- passive or active?